De Novo Design and Drug Release Applications of Fmoc-Diphenylalanine Self-Assembled Hydrogels

Introduction Background and Research Significance

In recent years, short peptide-based biomaterials with self-assembly characteristics have shown great potential in drug delivery systems and tissue engineering. These materials spontaneously form ordered nanostructures through intermolecular non-covalent interactions (such as π-π stacking, hydrogen bonding, and hydrophobic effects), among which the Fmoc (9-fluorenylmethoxycarbonyl) modified diphenylalanine (Fmoc-FF) system is particularly noteworthy. Although traditional Fmoc-FF hydrogels exhibit excellent mechanical properties and biocompatibility, issues such as harsh gelation conditions and slow kinetics limit their clinical applications. A joint research team from Fudan University rationally designed a new peptide-based hydrogel, Fmoc-FFRRVR, by introducing an arginine-arginine-valine-arginine (RRVR) hydrophilic segment into the Fmoc-FF sequence, achieving rapid gelation within seconds (only 2 seconds) along with controllable drug release functionality.

Material Design and Structural Characterization

The molecular design of Fmoc-FFRRVR fully considers the principle of balancing hydrophilicity/hydrophobicity. While retaining the core π-π stacking effect of Fmoc-FF, the introduction of RRVR significantly enhances molecular hydrophilicity. This was verified by circular dichroism (CD) analysis: characteristic negative peaks at 208 nm and 222 nm confirmed the formation of β-sheet secondary structures. Fluorescence emission spectra showed an emission peak at 428 nm further supporting ordered packing of fluorene groups. This molecular design allows for stable gel states under various physiologically relevant conditions (including PBS buffer solution at different pH levels).

Rheological tests indicate that the Fmoc-FFRRVR hydrogel exhibits typical viscoelastic behavior: storage modulus (G') consistently exceeds loss modulus (G''), while strain scanning demonstrates excellent reversible deformation capability. Notably, this material maintains structural integrity even after multiple shear-recovery cycles; its "shear-thinning-self-healing" property makes it highly suitable as an injectable drug carrier.

Drug Loading and Release Mechanism

As a drug delivery carrier, the Fmoc-FFRRVR hydrogel shows unique advantages. Using doxorubicin (DOX) as a model drug, infrared spectroscopy (FTIR) analysis revealed hydrogen bond interactions between amino groups in drug molecules and carboxylic acid groups in peptides; these intermolecular forces ensure high loading efficiency (~90%) while enabling pH-responsive release mechanisms. Under simulated tumor microenvironment conditions (pH 5.0), cumulative release over 72 hours reached 78.3%, significantly higher than that under physiological pH conditions (7.4), where it was only 42.6%. This differential release behavior arises from dissociation of hydrogen bond networks in acidic environments coupled with increased swelling degree of gels.

Confocal laser scanning microscopy observations show that DOX-loaded hydrogels effectively internalize when co-cultured with MDA-MB-231 breast cancer cells within just 2.5 hours—locating primarily within nuclear regions—highlighting time-dependent progressive patterns consistent with results from in vitro release experiments based on comparative fluorescence intensity distributions across different time points.

Application Prospects & Outlook

This study opens up new avenues for rational design regarding peptide-based hydrogels compared to traditional systems like FMOC– FF-RRVR not only retains superior mechanical performance alongside biocompatibility but also aligns better clinically due to rapid gelation plus environmental responsiveness features . Future research directions may focus on several aspects : firstly , incorporating diverse functional amino acid segments could allow further tuning towards both mechanical properties degradation kinetics ; secondly , exploring capabilities surrounding protein drugs’ loading /controlled-release ability(antibodies,growth factors etc.) ; lastly systematic evaluations must be conducted concerning pharmacodynamics biodistribution long-term safety assessments etc . This research has been published in Journal Materials Chemistry B guided collaboratively by Professor Yi Tao from Shanghai University Associate Professor Zhou Yifeng Shanghai Applied Technology University Professor Zhou Dongfang Southern Medical University providing significant theoretical basis technical support developing next-generation intelligent medication delivery systems.